1. Field of the Invention
The present invention relates to a pigment-containing heat-curable composition favorable for forming a colored image on the color filters for use in liquid crystal display devices (LCD's), solid-state imaging devices (CCD, CMOS, and others), and others, a color filter and an image-recording material using the pigment-containing heat-curable composition, and a method of producing the color filter by forming a pattern by dry etching.
2. Description of the Related Art
As methods for producing a color filter for use with a liquid crystal display device or a solid image pickup element, a dyeing methods, a printing methods, an electrodeposition methods, and a pigment dispersion methods are known.
In the pigment dispersion method, the color filter is produced by a photolithographic method using a colored radiation-sensitive composition prepared by dispersing a pigment in any one of various types of photosensitive compositions. The color filter produced by this method is stable with respect to light, heat and the like since the pigment is used. A high positional accuracy can be obtained in this method since patterning is performed by the photolithographic method and, accordingly, this method has widely been used as a method suitable for producing the color filter for a large screen and high fineness color display.
In a case in which the color filter is produced by the pigment dispersion method, the radiation-sensitive composition is first coated on a glass substrate by using, for example, a spin coater or a roll coater and, then, dried, to thereby form a coating film. Then, colored pixels are obtained by pattern-exposing and developing the thus-formed coating film. The color filter can be obtained by repeating such operation as described above by the number of different colors.
As for the pigment dispersion method, a method which uses a negative-type photosensitive composition using an alkali-soluble resin together with a photopolymerizable monomer and a photopolymerization initiator is proposed in each of, for example, JP-A Nos. 2-181704, 2-199403, 5-273411 and 7-140654.
In the increasing need for high-resolution of the color filter for solid-state imaging devices, a method of using a dye was proposed recently (for example, Japanese Patent Application Laid-Open (JP-A) No. 6-75375). However, such dye-containing heat-curable compositions had problems, for example, that they are normally inferior to those containing pigment in various properties such as light fastness, heat resistance, solubility, and coating uniformity. In addition, preparation of the color filter for solid-state imaging devices, which demand a film thickness of 1.5 μm or less and thus, addition of a colorant to the heat-curable composition in a greater amount, often caused a problem of extremely lower patterning efficiency because of insufficient adhesion to the substrate, insufficient hardening, and disappearance of the dye in the exposed portion.
Alternatively, the color filters by photolithography, which contains components other than the colorant such as binder resin, photopolymerizable compound, and initiator in some amounts, have a disadvantage of prohibiting reduction in the film thickness, independently of whether the colorant is a pigment or dye. However, there exists a strong demand recently for reduction in the thickness of color filter, for improvement in the image quality by reduction in shading.
In production of the photolithographic color filters, dry etching methods have been known as the methods effective in forming a thinner film suitable for forming a fine pattern. The dry etching methods, which have been used as the methods of forming a pattern on a colorant-deposited thin film (see, for example, JP-A No. 55-146406), allow production of a color filter having a film thickness of ½ or less of that of the photolithographic color filter, while the spectroscopic characteristics are preserved at the same level.
However, production of thin film by vapor deposition is always accompanied by contamination of the vapor deposition apparatus, which put a heavy load on production of color filter. In addition, the pattern formed is lower in adhesiveness to the lower flat film or the upper film because the pixels are formed only with a pigment or dye, which is also a reason for its low yield.